1. Field of the Invention
The present invention relates generally to a circuit including a negative differential resistance (NDR) device, and more particularly, to a circuit including an NDR device which includes a graphene channel.
2. Description of the Related Art
Negative differential resistance (NDR) is a unique property of some electrical circuits where an increase in the current entering a port results in a decreased voltage across the same port. This is in contrast to most electrical components with a positive resistance, which exhibit monotonically increasing electrical currents when the voltage is raised across the electrical ports.
Devices exhibiting negative resistance are particularly useful for applications at microwave frequencies. Negative resistivity is also essential and important in modern electrical applications, such as amplifiers, oscillators, mixers and impedance cancellation.
In contrast to a normally positive resistive device that dissipates energy, an element with negative resistance would generate energy when passing electrical currents. Therefore, absolute negative resistance does not theoretically exist as a discrete component.
In practice, NDR can be achieved in some diodes (e.g. tunneling diodes) in some part of their operating range. NDR can also be obtained in a sophisticated and controlled circuitry, such as an operational amplifier with properly designed feedback.
However, such NDR devices or circuits are typically built as standalone or independent components, and cannot be easily integrated with the rest of the circuits using wafer-scale fabrication processes. This is a problem because such on-chip circuit integration is advantageous and important in order to improve the operating performance (e.g. frequency) and lower the manufacturing cost.